Chapter-8
Tissue and Tissue System
Contents
Meristematic Tissue and its classification
Permanent Tissue and its classification
3 types of Tissue systems
Different types of vascular bundles
Internal structure of Monocot root and stem
Primary internal structure of Dicot stem
What is plant tissue ?
Multicellular organisms are made up of millions of cells. Cells are structural and functional units of life. They show divisions of labour and each cell
performs a particular function efficiently. Such cells are grouped together and are referred to as tissues.
Plant tissue is a group of cells which are similar in structure and origin and perform a similar function for the plant. Each plant tissue is specialized for a unique purpose ,and can be combined with other tissues to create organs such as flowers ,leaves, stems and roots.
Classification of plant tissue
A group of cells Tissue A group of tissue Tissue System A group of tissue system Organ A group of organs Plant body
Based on position, structure and function plant tissues are of two types:
1.Meristematic tissue
2.Permanent tissue
What is meant by Meristematic Tissue ?
The tissue of which the cells being divided to produce new cells or the cells retain the ability of being divided is called Meristematic tissue. The cells of these tissues are commonly called meristems.
Fig: A typical Meristematic Tissue
Thin Cell Wall
Properties of Meristematic tissue
• The meristematic tissue has the quality of self-renewal that is, the ability of being divided. Every time the cell divides, one cell remains identical to the parent cell .
• The meristematic tissue are living and thin-walled.
• The protoplasm of the cells is very dense.
• They possess a single, large and prominent nucleus.
• They have very small and few vacuoles.
• As cells are arranged compactly , no intercellular space is seen.
• The cells of the meristematic tissue are young and immature.
• They do not store food.
• They exhibit a very high metabolic activity.
Functions of Meristematic Tissue
1. Meristems are actively dividing tissues of the plant.
2. They are responsible for primary (elongation) and secondary (thickness) growth of the plant.
3. All new organs and their growth occur by the division of meristematic tissue.
4. Secondary tissues such as, wood, cork are also formed due to activity of meristematic tissue.
5. Permanent tissues are formed from this tissue.
6. Meristematic tissue also heals the wound of plant.
7. Helps in plant tissue culture.
Meristem
Based on origin
1. Promeristem 2. Primary
meristem 3. Secondary meristem
Based on location
1. Apical Meristem
2. Intercalary Meristem
3. Lateral Meristem
Based on cell division
1. Mass Meristem 2. Plate Meristem 3. Rib Meristem
Based on function
1. Protoderm 2. Procambium 3. Ground Meriste
Classification of Meristametic Tissue in a tabular form
Based on origin, meristematic tissues are of three types :
(1) Promeristem or Primordial Meristem : The promeristem originates from embryo and therefore , called primordial or embryonic meristem. It is present in the regions where an organ or a part of plant body is initiated. A group of initial cells that lay down the foundation of an organ or a plant part, is called Promeristem.
It occupies a small area at the tips of stem and root. Promeristem gives rise to all other meristems including the primary meristem.
(2) Primary Meristem : It is the meristem that is present right from the embryonic stage and continues to be active throughout the life of a plant. It is responsible for primary growth( in length) in the plant body. It gives rise to the primary permanent tissue of plant body. This meristem found at the root and stem apex.
(3) Secondary Meristem : It is the meristem that appears later in the life cycle of a plant . It develops by a process called dedifferentiation in the permanent tissues. It is responsible for the secondary
growth(in breath) of the plant body. Cork cambium and vascular cambium are the example of secondary meristem.
1. Apical Meristems – These meristems are located on the tip of the root, stem etc.
Function: They help in the growth of the root system as well as the shoot
system. Due to the activity of apical meristem the plant body keeps increasing in its length.
2. Intercalary Meristems – The intercalary meristems are located at the nodal zones between permanent tissues or the base of the leaves.
Function : The intercalary meristems help in increasing the length of the internode. It is also responsible for the formation of branches at the nodal zone.
3. Lateral Meristems – The lateral meristems are present on the lateral side of the stem and root of a plant.
Function : These meristems help in increasing the thickness of the plants. The vascular cambium and the cork cambium are good examples of a lateral
meristematic tissue.
Based on location Meristametic tissues are of three types :
Based on the cell division meristematic tissues are of three types:
1. Mass meristem : In mass meristem, the cells divide in all planes to form a cluster of cells without any regular order.
Function :
This type of tissue increases the density of plant to take part in the formation of cortex, pith, endoderm and developing sporangia.
2. Plate meristem : In this type of meristem, the cells divide in two planes . Function :
This type of meristem takes part in the formation of flat structure such as leaf formation without increasing thickness.
3. Rib meristem : In this type of meristem , the cells divide in one plane and are arranged in a row in a linear form.
Function :
This type of meristem plays an important role in the formation of young root, cortex and pith of young stems in higher plants.
Based on the function meristematic tissues are of three types:
1. Protoderm 2. Procambium
3. Ground meristem
• Protoderm:
• It is the outermost single layered meristematic tissue.
• It gives rise to epidermis layer.
• It provides the outer protective covering and gives protection from mechanical injury.
• Procambium:
• It is the innermost meristematic tissue.
• It gives rise to vascular tissue ( xylem and phloem)
• Helps in transportation of water and nutrition.
• Ground meristem:
• It consists of several layers of meristematic cells beneath the protoderm.
• It gives rise to cortex, hypodermis (in monocot),endodermis, pericycle, pith and pith rays.
All tissues are originated from apical meristem
The meristematic tissue which is located at the root and shoot apex is called apical meristematic tissue.
No other tissue except apical meristem is found at the transverse section of the tip of root and shoot apex. But just a little behind of this part, if a transverse section is taken not only the meristem, but also the other tissues like epidermis, cortex, pericycle, vascular bundle, pith, pith rays etc are seen. All tissues of root and stem like epidermis
(epiblema, in root), hypodermis, cortex, pericycle, xylem, phloem, vascular
cambium, pith, pith rays are developed due to the gradual development of
apical meristem. There are few theories found regarding the origin of all other
tissues from apical meristem. Fig: Different types of Meristematic Tissue
Ground meristem Epidermal
tissue system Protoderm
Ground tissue system Vascular tissue system
Procambium
L.S. of apical meristem T.S. of apical meristem
Apical Meristem is the source of all other tissues
Protoderm Primary Tissue
Secondary Tissue
Dermal Tissue Epidermis
Dermal cell, Stomata, Stem hair, Root hair, Etc.
Ground Meistem Ground Tissue
Collenchyma, Sclerenchyma,
Parenchyma
Procambium Vascular Tissue
Xylem Residual Phloem
Procambium Vascular Cambium
Cork cambium Cork
Secondary Xylem Secondary Phloem
THANK YOU H.W.
1. Learn the properties and functions of meristematic tissue.
2. Learn the classification of meristematic tissue based on origin and location, with diagram.
